/* trees.c -- output deflated data using Huffman coding
 * Copyright (C) 1995-1998 Jean-loup Gailly
 * For conditions of distribution and use, see copyright notice in zlib.h 
 */

/*
 *  ALGORITHM
 *
 *      The "deflation" process uses several Huffman trees. The more
 *      common source values are represented by shorter bit sequences.
 *
 *      Each code tree is stored in a compressed form which is itself
 * a Huffman encoding of the lengths of all the code strings (in
 * ascending order by source values).  The actual code strings are
 * reconstructed from the lengths in the inflate process, as described
 * in the deflate specification.
 *
 *  REFERENCES
 *
 *      Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
 *      Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
 *
 *      Storer, James A.
 *          Data Compression:  Methods and Theory, pp. 49-50.
 *          Computer Science Press, 1988.  ISBN 0-7167-8156-5.
 *
 *      Sedgewick, R.
 *          Algorithms, p290.
 *          Addison-Wesley, 1983. ISBN 0-201-06672-6.
 */

/* @(#) $Id$ */

/* #define GEN_TREES_H */

#include "deflate.h"

#ifdef DEBUG
#  include <ctype.h>
#endif

/* ===========================================================================
 * Constants
 */

#define MAX_BL_BITS 7
/* Bit length codes must not exceed MAX_BL_BITS bits */

#define END_BLOCK 256
/* end of block literal code */

#define REP_3_6      16
/* repeat previous bit length 3-6 times (2 bits of repeat count) */

#define REPZ_3_10    17
/* repeat a zero length 3-10 times  (3 bits of repeat count) */

#define REPZ_11_138  18
/* repeat a zero length 11-138 times  (7 bits of repeat count) */

   local const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
   = {0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0};

   local const int extra_dbits[D_CODES] /* extra bits for each distance code */
   = {0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13};

   local const int extra_blbits[BL_CODES]/* extra bits for each bit length code */
   = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};

   local const uch bl_order[BL_CODES]
   = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
/* The lengths of the bit length codes are sent in order of decreasing
 * probability, to avoid transmitting the lengths for unused bit length codes.
 */

#define Buf_size (8 * 2*sizeof(char))
/* Number of bits used within bi_buf. (bi_buf might be implemented on
 * more than 16 bits on some systems.)
 */

/* ===========================================================================
 * Local data. These are initialized only once.
 */

#define DIST_CODE_LEN  512 /* see definition of array dist_code below */

#if defined(GEN_TREES_H) || !defined(STDC)
/* non ANSI compilers may not accept trees.h */

local ct_data static_ltree[L_CODES+2];
/* The static literal tree. Since the bit lengths are imposed, there is no
 * need for the L_CODES extra codes used during heap construction. However
 * The codes 286 and 287 are needed to build a canonical tree (see _tr_init
 * below).
 */

local ct_data static_dtree[D_CODES];
/* The static distance tree. (Actually a trivial tree since all codes use
 * 5 bits.)
 */

uch _dist_code[DIST_CODE_LEN];
/* Distance codes. The first 256 values correspond to the distances
 * 3 .. 258, the last 256 values correspond to the top 8 bits of
 * the 15 bit distances.
 */

uch _length_code[MAX_MATCH-MIN_MATCH+1];
/* length code for each normalized match length (0 == MIN_MATCH) */

local int base_length[LENGTH_CODES];
/* First normalized length for each code (0 = MIN_MATCH) */

local int base_dist[D_CODES];
/* First normalized distance for each code (0 = distance of 1) */

#else
#  include "trees.h"
#endif /* GEN_TREES_H */

   struct static_tree_desc_s {
      const ct_data *static_tree;  /* static tree or NULL */
      const intf *extra_bits;      /* extra bits for each code or NULL */
      int     extra_base;          /* base index for extra_bits */
      int     elems;               /* max number of elements in the tree */
      int     max_length;          /* max bit length for the codes */
   };

   local static_tree_desc  static_l_desc =
   {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};

   local static_tree_desc  static_d_desc =
   {static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};

   local static_tree_desc  static_bl_desc =
   {(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS};

/* ===========================================================================
 * Local (static) routines in this file.
 */

   local void tr_static_init OF((void));
   local void init_block     OF((deflate_state *s));
   local void pqdownheap     OF((deflate_state *s, ct_data *tree, int k));
   local void gen_bitlen     OF((deflate_state *s, tree_desc *desc));
   local void gen_codes      OF((ct_data *tree, int max_code, ushf *bl_count));
   local void build_tree     OF((deflate_state *s, tree_desc *desc));
   local void scan_tree      OF((deflate_state *s, ct_data *tree, int max_code));
   local void send_tree      OF((deflate_state *s, ct_data *tree, int max_code));
   local int  build_bl_tree  OF((deflate_state *s));
   local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
                              int blcodes));
   local void compress_block OF((deflate_state *s, ct_data *ltree,
                              ct_data *dtree));
   local void set_data_type  OF((deflate_state *s));
   local unsigned bi_reverse OF((unsigned value, int length));
   local void bi_windup      OF((deflate_state *s));
   local void bi_flush       OF((deflate_state *s));
   local void copy_block     OF((deflate_state *s, charf *buf, unsigned len,
                              int header));

#ifdef GEN_TREES_H
local void gen_trees_header OF((void));
#endif

#ifndef DEBUG
#  define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
   /* Send a code of the given tree. c and tree must not have side effects */

#else /* DEBUG */
#  define send_code(s, c, tree) \
     { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
       send_bits(s, tree[c].Code, tree[c].Len); }
#endif

/* ===========================================================================
 * Output a short LSB first on the stream.
 * IN assertion: there is enough room in pendingBuf.
 */
#define put_short(s, w) { \
    put_byte(s, (uch)((w) & 0xff)); \
    put_byte(s, (uch)((ush)(w) >> 8)); \
}

/* ===========================================================================
 * Send a value on a given number of bits.
 * IN assertion: length <= 16 and value fits in length bits.
 */
#ifdef DEBUG
local void send_bits      OF((deflate_state *s, int value, int length));

local void send_bits(s, value, length)
    deflate_state *s;
    int value;  /* value to send */
    int length; /* number of bits */
{
    Tracevv((stderr," l %2d v %4x ", length, value));
    Assert(length > 0 && length <= 15, "invalid length");
    s->bits_sent += (ulg)length;

    /* If not enough room in bi_buf, use (valid) bits from bi_buf and
     * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
     * unused bits in value.
     */
    if (s->bi_valid > (int)Buf_size - length) {
        s->bi_buf |= (value << s->bi_valid);
        put_short(s, s->bi_buf);
        s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
        s->bi_valid += length - Buf_size;
    } else {
        s->bi_buf |= value << s->bi_valid;
        s->bi_valid += length;
    }
}
#else /* !DEBUG */

#define send_bits(s, value, length) \
{ int len = length;\
  if (s->bi_valid > (int)Buf_size - len) {\
    int val = value;\
    s->bi_buf |= (val << s->bi_valid);\
    put_short(s, s->bi_buf);\
    s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
    s->bi_valid += len - Buf_size;\
  } else {\
    s->bi_buf |= (value) << s->bi_valid;\
    s->bi_valid += len;\
  }\
}
#endif /* DEBUG */


#define MAX(a,b) (a >= b ? a : b)
/* the arguments must not have side effects */

/* ===========================================================================
 * Initialize the various 'constant' tables.
 */
    local void tr_static_init()
   {
   #if defined(GEN_TREES_H) || !defined(STDC)
    static int static_init_done = 0;
    int n;        /* iterates over tree elements */
    int bits;     /* bit counter */
    int length;   /* length value */
    int code;     /* code value */
    int dist;     /* distance index */
    ush bl_count[MAX_BITS+1];
    /* number of codes at each bit length for an optimal tree */
   
    if (static_init_done) return;
   
    /* For some embedded targets, global variables are not initialized: */
    static_l_desc.static_tree = static_ltree;
    static_l_desc.extra_bits = extra_lbits;
    static_d_desc.static_tree = static_dtree;
    static_d_desc.extra_bits = extra_dbits;
    static_bl_desc.extra_bits = extra_blbits;
   
    /* Initialize the mapping length (0..255) -> length code (0..28) */
    length = 0;
    for (code = 0; code < LENGTH_CODES-1; code++) {
        base_length[code] = length;
        for (n = 0; n < (1<<extra_lbits[code]); n++) {
            _length_code[length++] = (uch)code;
        }
    }
    Assert (length == 256, "tr_static_init: length != 256");
    /* Note that the length 255 (match length 258) can be represented
     * in two different ways: code 284 + 5 bits or code 285, so we
     * overwrite length_code[255] to use the best encoding:
     */
    _length_code[length-1] = (uch)code;
   
    /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
    dist = 0;
    for (code = 0 ; code < 16; code++) {
        base_dist[code] = dist;
        for (n = 0; n < (1<<extra_dbits[code]); n++) {
            _dist_code[dist++] = (uch)code;
        }
    }
    Assert (dist == 256, "tr_static_init: dist != 256");
    dist >>= 7; /* from now on, all distances are divided by 128 */
    for ( ; code < D_CODES; code++) {
        base_dist[code] = dist << 7;
        for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
            _dist_code[256 + dist++] = (uch)code;
        }
    }
    Assert (dist == 256, "tr_static_init: 256+dist != 512");
   
    /* Construct the codes of the static literal tree */
    for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
    n = 0;
    while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
    while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
    while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
    while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
    /* Codes 286 and 287 do not exist, but we must include them in the
     * tree construction to get a canonical Huffman tree (longest code
     * all ones)
     */
    gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
   
    /* The static distance tree is trivial: */
    for (n = 0; n < D_CODES; n++) {
        static_dtree[n].Len = 5;
        static_dtree[n].Code = bi_reverse((unsigned)n, 5);
    }
    static_init_done = 1;
   
   #  ifdef GEN_TREES_H
    gen_trees_header();
   #  endif
   #endif /* defined(GEN_TREES_H) || !defined(STDC) */
   }

/* ===========================================================================
 * Genererate the file trees.h describing the static trees.
 */
#ifdef GEN_TREES_H
#  ifndef DEBUG
#    include <stdio.h>
#  endif

#  define SEPARATOR(i, last, width) \
      ((i) == (last)? "\n};\n\n" :    \
       ((i) % (width) == (width)-1 ? ",\n" : ", "))

void gen_trees_header()
{
    FILE *header = fopen("trees.h", "w");
    int i;

    Assert (header != NULL, "Can't open trees.h");
    fprintf(header,
	    "/* header created automatically with -DGEN_TREES_H */\n\n");

    fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n");
    for (i = 0; i < L_CODES+2; i++) {
	fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code,
		static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));
    }

    fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n");
    for (i = 0; i < D_CODES; i++) {
	fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code,
		static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));
    }

    fprintf(header, "const uch _dist_code[DIST_CODE_LEN] = {\n");
    for (i = 0; i < DIST_CODE_LEN; i++) {
	fprintf(header, "%2u%s", _dist_code[i],
		SEPARATOR(i, DIST_CODE_LEN-1, 20));
    }

    fprintf(header, "const uch _length_code[MAX_MATCH-MIN_MATCH+1]= {\n");
    for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) {
	fprintf(header, "%2u%s", _length_code[i],
		SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));
    }

    fprintf(header, "local const int base_length[LENGTH_CODES] = {\n");
    for (i = 0; i < LENGTH_CODES; i++) {
	fprintf(header, "%1u%s", base_length[i],
		SEPARATOR(i, LENGTH_CODES-1, 20));
    }

    fprintf(header, "local const int base_dist[D_CODES] = {\n");
    for (i = 0; i < D_CODES; i++) {
	fprintf(header, "%5u%s", base_dist[i],
		SEPARATOR(i, D_CODES-1, 10));
    }

    fclose(header);
}
#endif /* GEN_TREES_H */

/* ===========================================================================
 * Initialize the tree data structures for a new zlib stream.
 */
    void _tr_init(deflate_state *s){
      tr_static_init();
   
      s->l_desc.dyn_tree = s->dyn_ltree;
      s->l_desc.stat_desc = &static_l_desc;
   
      s->d_desc.dyn_tree = s->dyn_dtree;
      s->d_desc.stat_desc = &static_d_desc;
   
      s->bl_desc.dyn_tree = s->bl_tree;
      s->bl_desc.stat_desc = &static_bl_desc;
   
      s->bi_buf = 0;
      s->bi_valid = 0;
      s->last_eob_len = 8; /* enough lookahead for inflate */
   #ifdef DEBUG
    s->compressed_len = 0L;
    s->bits_sent = 0L;
   #endif
   
    /* Initialize the first block of the first file: */
      init_block(s);
   }

/* ===========================================================================
 * Initialize a new block.
 */
    local void init_block(deflate_state *s){
      int n; /* iterates over tree elements */
   
    /* Initialize the trees. */
      for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
      for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
      for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
   
      s->dyn_ltree[END_BLOCK].Freq = 1;
      s->opt_len = s->static_len = 0L;
      s->last_lit = s->matches = 0;
   }

#define SMALLEST 1
/* Index within the heap array of least frequent node in the Huffman tree */


/* ===========================================================================
 * Remove the smallest element from the heap and recreate the heap with
 * one less element. Updates heap and heap_len.
 */
#define pqremove(s, tree, top) \
{\
    top = s->heap[SMALLEST]; \
    s->heap[SMALLEST] = s->heap[s->heap_len--]; \
    pqdownheap(s, tree, SMALLEST); \
}

/* ===========================================================================
 * Compares to subtrees, using the tree depth as tie breaker when
 * the subtrees have equal frequency. This minimizes the worst case length.
 */
#define smaller(tree, n, m, depth) \
   (tree[n].Freq < tree[m].Freq || \
   (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))

/* ===========================================================================
 * Restore the heap property by moving down the tree starting at node k,
 * exchanging a node with the smallest of its two sons if necessary, stopping
 * when the heap property is re-established (each father smaller than its
 * two sons).
 */
    local void pqdownheap(
    deflate_state *s,
    ct_data *tree,  /* the tree to restore */
    int k)               /* node to move down */
   {
      int v = s->heap[k];
      int j = k << 1;  /* left son of k */
      while (j <= s->heap_len) {
        /* Set j to the smallest of the two sons: */
         if (j < s->heap_len &&
            smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
            j++;
         }
        /* Exit if v is smaller than both sons */
         if (smaller(tree, v, s->heap[j], s->depth)) 
            break;
      
        /* Exchange v with the smallest son */
         s->heap[k] = s->heap[j];  k = j;
      
        /* And continue down the tree, setting j to the left son of k */
         j <<= 1;
      }
      s->heap[k] = v;
   }

/* ===========================================================================
 * Compute the optimal bit lengths for a tree and update the total bit length
 * for the current block.
 * IN assertion: the fields freq and dad are set, heap[heap_max] and
 *    above are the tree nodes sorted by increasing frequency.
 * OUT assertions: the field len is set to the optimal bit length, the
 *     array bl_count contains the frequencies for each bit length.
 *     The length opt_len is updated; static_len is also updated if stree is
 *     not null.
 */
    local void gen_bitlen(
    deflate_state *s,
    tree_desc *desc)    /* the tree descriptor */
   {
      ct_data *tree        = desc->dyn_tree;
      int max_code         = desc->max_code;
      const ct_data *stree = desc->stat_desc->static_tree;
      const intf *extra    = desc->stat_desc->extra_bits;
      int base             = desc->stat_desc->extra_base;
      int max_length       = desc->stat_desc->max_length;
      int h;              /* heap index */
      int n, m;           /* iterate over the tree elements */
      int bits;           /* bit length */
      int xbits;          /* extra bits */
      ush f;              /* frequency */
      int overflow = 0;   /* number of elements with bit length too large */
   
      for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
   
    /* In a first pass, compute the optimal bit lengths (which may
     * overflow in the case of the bit length tree).
     */
      tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
   
      for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
         n = s->heap[h];
         bits = tree[tree[n].Dad].Len + 1;
         if (bits > max_length) bits = max_length, overflow++;
         tree[n].Len = (ush)bits;
        /* We overwrite tree[n].Dad which is no longer needed */
      
         if (n > max_code) 
            continue; /* not a leaf node */
      
         s->bl_count[bits]++;
         xbits = 0;
         if (n >= base) xbits = extra[n-base];
         f = tree[n].Freq;
         s->opt_len += (ulg)f * (bits + xbits);
         if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
      }
      if (overflow == 0) 
         return;
   
    Trace((stderr,"\nbit length overflow\n"));
    /* This happens for example on obj2 and pic of the Calgary corpus */
   
    /* Find the first bit length which could increase: */
      do {
         bits = max_length-1;
         while (s->bl_count[bits] == 0) bits--;
         s->bl_count[bits]--;      /* move one leaf down the tree */
         s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
         s->bl_count[max_length]--;
        /* The brother of the overflow item also moves one step up,
         * but this does not affect bl_count[max_length]
         */
         overflow -= 2;
      } while (overflow > 0);
   
    /* Now recompute all bit lengths, scanning in increasing frequency.
     * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
     * lengths instead of fixing only the wrong ones. This idea is taken
     * from 'ar' written by Haruhiko Okumura.)
     */
      for (bits = max_length; bits != 0; bits--) {
         n = s->bl_count[bits];
         while (n != 0) {
            m = s->heap[--h];
            if (m > max_code) 
               continue;
            if (tree[m].Len != (unsigned) bits) {
                Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
               s->opt_len += ((long)bits - (long)tree[m].Len)
                              *(long)tree[m].Freq;
               tree[m].Len = (ush)bits;
            }
            n--;
         }
      }
   }

/* ===========================================================================
 * Generate the codes for a given tree and bit counts (which need not be
 * optimal).
 * IN assertion: the array bl_count contains the bit length statistics for
 * the given tree and the field len is set for all tree elements.
 * OUT assertion: the field code is set for all tree elements of non
 *     zero code length.
 */
    local void gen_codes (
    ct_data *tree,             /* the tree to decorate */
    int max_code,              /* largest code with non zero frequency */
    ushf *bl_count)            /* number of codes at each bit length */
   {
      ush next_code[MAX_BITS+1]; /* next code value for each bit length */
      ush code = 0;              /* running code value */
      int bits;                  /* bit index */
      int n;                     /* code index */
   
    /* The distribution counts are first used to generate the code values
     * without bit reversal.
     */
      for (bits = 1; bits <= MAX_BITS; bits++) {
         next_code[bits] = code = (code + bl_count[bits-1]) << 1;
      }
    /* Check that the bit counts in bl_count are consistent. The last code
     * must be all ones.
     */
    Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
            "inconsistent bit counts");
    Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
   
      for (n = 0;  n <= max_code; n++) {
         int len = tree[n].Len;
         if (len == 0) 
            continue;
        /* Now reverse the bits */
         tree[n].Code = bi_reverse(next_code[len]++, len);
      
        Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
             n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
      }
   }

/* ===========================================================================
 * Construct one Huffman tree and assigns the code bit strings and lengths.
 * Update the total bit length for the current block.
 * IN assertion: the field freq is set for all tree elements.
 * OUT assertions: the fields len and code are set to the optimal bit length
 *     and corresponding code. The length opt_len is updated; static_len is
 *     also updated if stree is not null. The field max_code is set.
 */
    local void build_tree(
    deflate_state *s,
    tree_desc *desc) /* the tree descriptor */
   {
      ct_data *tree         = desc->dyn_tree;
      const ct_data *stree  = desc->stat_desc->static_tree;
      int elems             = desc->stat_desc->elems;
      int n, m;          /* iterate over heap elements */
      int max_code = -1; /* largest code with non zero frequency */
      int node;          /* new node being created */
   
    /* Construct the initial heap, with least frequent element in
     * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
     * heap[0] is not used.
     */
      s->heap_len = 0, s->heap_max = HEAP_SIZE;
   
      for (n = 0; n < elems; n++) {
         if (tree[n].Freq != 0) {
            s->heap[++(s->heap_len)] = max_code = n;
            s->depth[n] = 0;
         } 
         else {
            tree[n].Len = 0;
         }
      }
   
    /* The pkzip format requires that at least one distance code exists,
     * and that at least one bit should be sent even if there is only one
     * possible code. So to avoid special checks later on we force at least
     * two codes of non zero frequency.
     */
      while (s->heap_len < 2) {
         node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
         tree[node].Freq = 1;
         s->depth[node] = 0;
         s->opt_len--; 
         if (stree) s->static_len -= stree[node].Len;
        /* node is 0 or 1 so it does not have extra bits */
      }
      desc->max_code = max_code;
   
    /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
     * establish sub-heaps of increasing lengths:
     */
      for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
   
    /* Construct the Huffman tree by repeatedly combining the least two
     * frequent nodes.
     */
      node = elems;              /* next internal node of the tree */
      do {
         pqremove(s, tree, n);  /* n = node of least frequency */
         m = s->heap[SMALLEST]; /* m = node of next least frequency */
      
         s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
         s->heap[--(s->heap_max)] = m;
      
        /* Create a new node father of n and m */
         tree[node].Freq = tree[n].Freq + tree[m].Freq;
         s->depth[node] = (uch) (MAX(s->depth[n], s->depth[m]) + 1);
         tree[n].Dad = tree[m].Dad = (ush)node;
      #ifdef DUMP_BL_TREE
        if (tree == s->bl_tree) {
            fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
                    node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
        }
      #endif
        /* and insert the new node in the heap */
         s->heap[SMALLEST] = node++;
         pqdownheap(s, tree, SMALLEST);
      
      } while (s->heap_len >= 2);
   
      s->heap[--(s->heap_max)] = s->heap[SMALLEST];
   
    /* At this point, the fields freq and dad are set. We can now
     * generate the bit lengths.
     */
      gen_bitlen(s, (tree_desc *)desc);
   
    /* The field len is now set, we can generate the bit codes */
      gen_codes ((ct_data *)tree, max_code, s->bl_count);
   }

/* ===========================================================================
 * Scan a literal or distance tree to determine the frequencies of the codes
 * in the bit length tree.
 */
    local void scan_tree (
    deflate_state *s,
    ct_data *tree,   /* the tree to be scanned */
    int max_code)    /* and its largest code of non zero frequency */
   {
      int n;                     /* iterates over all tree elements */
      int prevlen = -1;          /* last emitted length */
      int curlen;                /* length of current code */
      int nextlen = tree[0].Len; /* length of next code */
      int count = 0;             /* repeat count of the current code */
      int max_count = 7;         /* max repeat count */
      int min_count = 4;         /* min repeat count */
   
      if (nextlen == 0) max_count = 138, min_count = 3;
      tree[max_code+1].Len = (ush)0xffff; /* guard */
   
      for (n = 0; n <= max_code; n++) {
         curlen = nextlen; nextlen = tree[n+1].Len;
         if (++count < max_count && curlen == nextlen) {
            continue;
         } 
         else if (count < min_count) {
            s->bl_tree[curlen].Freq += count;
         } 
         else if (curlen != 0) {
            if (curlen != prevlen) s->bl_tree[curlen].Freq++;
            s->bl_tree[REP_3_6].Freq++;
         } 
         else if (count <= 10) {
            s->bl_tree[REPZ_3_10].Freq++;
         } 
         else {
            s->bl_tree[REPZ_11_138].Freq++;
         }
         count = 0; prevlen = curlen;
         if (nextlen == 0) {
            max_count = 138, min_count = 3;
         } 
         else if (curlen == nextlen) {
            max_count = 6, min_count = 3;
         } 
         else {
            max_count = 7, min_count = 4;
         }
      }
   }

/* ===========================================================================
 * Send a literal or distance tree in compressed form, using the codes in
 * bl_tree.
 */
    local void send_tree (
    deflate_state *s,
    ct_data *tree, /* the tree to be scanned */
    int max_code)       /* and its largest code of non zero frequency */
   {
      int n;                     /* iterates over all tree elements */
      int prevlen = -1;          /* last emitted length */
      int curlen;                /* length of current code */
      int nextlen = tree[0].Len; /* length of next code */
      int count = 0;             /* repeat count of the current code */
      int max_count = 7;         /* max repeat count */
      int min_count = 4;         /* min repeat count */
   
    /* tree[max_code+1].Len = -1; */  /* guard already set */
      if (nextlen == 0) max_count = 138, min_count = 3;
   
      for (n = 0; n <= max_code; n++) {
         curlen = nextlen; nextlen = tree[n+1].Len;
         if (++count < max_count && curlen == nextlen) {
            continue;
         } 
         else if (count < min_count) {
            do { 
               send_code(s, curlen, s->bl_tree); } while (--count != 0);
         
         } 
         else if (curlen != 0) {
            if (curlen != prevlen) {
               send_code(s, curlen, s->bl_tree); count--;
            }
            Assert(count >= 3 && count <= 6, " 3_6?");
            send_code(s, REP_3_6, s->bl_tree); 
            send_bits(s, count-3, 2);
         
         } 
         else if (count <= 10) {
            send_code(s, REPZ_3_10, s->bl_tree); 
            send_bits(s, count-3, 3);
         
         } 
         else {
            send_code(s, REPZ_11_138, s->bl_tree); 
            send_bits(s, count-11, 7);
         }
         count = 0; prevlen = curlen;
         if (nextlen == 0) {
            max_count = 138, min_count = 3;
         } 
         else if (curlen == nextlen) {
            max_count = 6, min_count = 3;
         } 
         else {
            max_count = 7, min_count = 4;
         }
      }
   }

/* ===========================================================================
 * Construct the Huffman tree for the bit lengths and return the index in
 * bl_order of the last bit length code to send.
 */
    local int build_bl_tree(deflate_state *s){
      int max_blindex;  /* index of last bit length code of non zero freq */
   
    /* Determine the bit length frequencies for literal and distance trees */
      scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
      scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
   
    /* Build the bit length tree: */
      build_tree(s, (tree_desc *)(&(s->bl_desc)));
    /* opt_len now includes the length of the tree representations, except
     * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
     */
   
    /* Determine the number of bit length codes to send. The pkzip format
     * requires that at least 4 bit length codes be sent. (appnote.txt says
     * 3 but the actual value used is 4.)
     */
      for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
         if (s->bl_tree[bl_order[max_blindex]].Len != 0) 
            break;
      }
    /* Update opt_len to include the bit length tree and counts */
      s->opt_len += 3*(max_blindex+1) + 5+5+4;
    Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
            s->opt_len, s->static_len));
   
      return max_blindex;
   }

/* ===========================================================================
 * Send the header for a block using dynamic Huffman trees: the counts, the
 * lengths of the bit length codes, the literal tree and the distance tree.
 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
 */
    local void send_all_trees(deflate_state *s, int lcodes, int dcodes, int blcodes){
      int rank;                    /* index in bl_order */
   
    Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
    Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
            "too many codes");
    Tracev((stderr, "\nbl counts: "));
      send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
      send_bits(s, dcodes-1,   5);
      send_bits(s, blcodes-4,  4); /* not -3 as stated in appnote.txt */
      for (rank = 0; rank < blcodes; rank++) {
        Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
         send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
      }
    Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
   
      send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
    Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
   
      send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
    Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
   }

/* ===========================================================================
 * Send a stored block
 */
    void _tr_stored_block(
    deflate_state *s,
    charf *buf,       /* input block */
    ulg stored_len,   /* length of input block */
    int eof)          /* true if this is the last block for a file */
   {
      send_bits(s, (STORED_BLOCK<<1)+eof, 3);  /* send block type */
   #ifdef DEBUG
    s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
    s->compressed_len += (stored_len + 4) << 3;
   #endif
      copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
   }

/* ===========================================================================
 * Send one empty static block to give enough lookahead for inflate.
 * This takes 10 bits, of which 7 may remain in the bit buffer.
 * The current inflate code requires 9 bits of lookahead. If the
 * last two codes for the previous block (real code plus EOB) were coded
 * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
 * the last real code. In this case we send two empty static blocks instead
 * of one. (There are no problems if the previous block is stored or fixed.)
 * To simplify the code, we assume the worst case of last real code encoded
 * on one bit only.
 */
    void _tr_align(deflate_state *s){
      send_bits(s, STATIC_TREES<<1, 3);
      send_code(s, END_BLOCK, static_ltree);
   #ifdef DEBUG
    s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
   #endif
      bi_flush(s);
    /* Of the 10 bits for the empty block, we have already sent
     * (10 - bi_valid) bits. The lookahead for the last real code (before
     * the EOB of the previous block) was thus at least one plus the length
     * of the EOB plus what we have just sent of the empty static block.
     */
      if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
         send_bits(s, STATIC_TREES<<1, 3);
         send_code(s, END_BLOCK, static_ltree);
      #ifdef DEBUG
        s->compressed_len += 10L;
      #endif
         bi_flush(s);
      }
      s->last_eob_len = 7;
   }

/* ===========================================================================
 * Determine the best encoding for the current block: dynamic trees, static
 * trees or store, and output the encoded block to the zip file.
 */
    void _tr_flush_block(
    deflate_state *s,
    charf *buf,       /* input block, or NULL if too old */
    ulg stored_len,   /* length of input block */
    int eof)          /* true if this is the last block for a file */
   {
      ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
      int max_blindex = 0;  /* index of last bit length code of non zero freq */
   
    /* Build the Huffman trees unless a stored block is forced */
      if (s->level > 0) {
      
      /* Check if the file is ascii or binary */
         if (s->data_type == Z_UNKNOWN) set_data_type(s);
      
      /* Construct the literal and distance trees */
         build_tree(s, (tree_desc *)(&(s->l_desc)));
      Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
      s->static_len));
      
         build_tree(s, (tree_desc *)(&(s->d_desc)));
      Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
      s->static_len));
      /* At this point, opt_len and static_len are the total bit lengths of
      * the compressed block data, excluding the tree representations.
      */
      
      /* Build the bit length tree for the above two trees, and get the index
      * in bl_order of the last bit length code to send.
      */
         max_blindex = build_bl_tree(s);
      
      /* Determine the best encoding. Compute first the block length in bytes*/
         opt_lenb = (s->opt_len+3+7)>>3;
         static_lenb = (s->static_len+3+7)>>3;
      
      Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
      opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
      s->last_lit));
      
         if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
      
      } 
      else {
        Assert(buf != (char*)0, "lost buf");
         opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
      }
   
   #ifdef FORCE_STORED
    if (buf != (char*)0) { /* force stored block */
   #else
      if (stored_len+4 <= opt_lenb && buf != (char*)0) {
                       /* 4: two words for the lengths */
      #endif
        /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
         * Otherwise we can't have processed more than WSIZE input bytes since
         * the last block flush, because compression would have been
         * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
         * transform a block into a stored block.
         */
         _tr_stored_block(s, buf, stored_len, eof);
      
      #ifdef FORCE_STATIC
      } else if (static_lenb >= 0) { /* force static trees */
      #else
      } 
      else if (static_lenb == opt_lenb) {
      #endif
         send_bits(s, (STATIC_TREES<<1)+eof, 3);
         compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
      #ifdef DEBUG
        s->compressed_len += 3 + s->static_len;
      #endif
      } 
      else {
         send_bits(s, (DYN_TREES<<1)+eof, 3);
         send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
                       max_blindex+1);
         compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
      #ifdef DEBUG
        s->compressed_len += 3 + s->opt_len;
      #endif
      }
    Assert (s->compressed_len == s->bits_sent, "bad compressed size");
    /* The above check is made mod 2^32, for files larger than 512 MB
     * and uLong implemented on 32 bits.
     */
      init_block(s);
   
      if (eof) {
         bi_windup(s);
      #ifdef DEBUG
        s->compressed_len += 7;  /* align on byte boundary */
      #endif
      }
    Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
           s->compressed_len-7*eof));
   }

/* ===========================================================================
 * Save the match info and tally the frequency counts. Return true if
 * the current block must be flushed.
 */
    int _tr_tally (
    deflate_state *s,
    unsigned dist,  /* distance of matched string */
    unsigned lc)    /* match length-MIN_MATCH or unmatched char (if dist==0) */
   {
      s->d_buf[s->last_lit] = (ush)dist;
      s->l_buf[s->last_lit++] = (uch)lc;
      if (dist == 0) {
        /* lc is the unmatched char */
         s->dyn_ltree[lc].Freq++;
      } 
      else {
         s->matches++;
        /* Here, lc is the match length - MIN_MATCH */
         dist--;             /* dist = match distance - 1 */
        Assert((ush)dist < (ush)MAX_DIST(s) &&
               (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
               (ush)d_code(dist) < (ush)D_CODES,  "_tr_tally: bad match");
      
         s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++;
         s->dyn_dtree[d_code(dist)].Freq++;
      }
   
   #ifdef TRUNCATE_BLOCK
    /* Try to guess if it is profitable to stop the current block here */
    if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
        /* Compute an upper bound for the compressed length */
        ulg out_length = (ulg)s->last_lit*8L;
        ulg in_length = (ulg)((long)s->strstart - s->block_start);
        int dcode;
        for (dcode = 0; dcode < D_CODES; dcode++) {
            out_length += (ulg)s->dyn_dtree[dcode].Freq *
                (5L+extra_dbits[dcode]);
        }
        out_length >>= 3;
        Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
               s->last_lit, in_length, out_length,
               100L - out_length*100L/in_length));
        if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
    }
   #endif
      return (s->last_lit == s->lit_bufsize-1);
    /* We avoid equality with lit_bufsize because of wraparound at 64K
     * on 16 bit machines and because stored blocks are restricted to
     * 64K-1 bytes.
     */
   }

/* ===========================================================================
 * Send the block data compressed using the given Huffman trees
 */
    local void compress_block(deflate_state *s,
    ct_data *ltree, /* literal tree */
    ct_data *dtree) /* distance tree */
   {
      unsigned dist;      /* distance of matched string */
      int lc;             /* match length or unmatched char (if dist == 0) */
      unsigned lx = 0;    /* running index in l_buf */
      unsigned code;      /* the code to send */
      int extra;          /* number of extra bits to send */
   
      if (s->last_lit != 0) 
         do {
            dist = s->d_buf[lx];
            lc = s->l_buf[lx++];
            if (dist == 0) {
               send_code(s, lc, ltree); /* send a literal byte */
            Tracecv(isgraph(lc), (stderr," '%c' ", lc));
            } 
            else {
            /* Here, lc is the match length - MIN_MATCH */
               code = _length_code[lc];
               send_code(s, code+LITERALS+1, ltree); /* send the length code */
               extra = extra_lbits[code];
               if (extra != 0) {
                  lc -= base_length[code];
                  send_bits(s, lc, extra);       /* send the extra length bits */
               }
               dist--; /* dist is now the match distance - 1 */
               code = d_code(dist);
            Assert (code < D_CODES, "bad d_code");
            
               send_code(s, code, dtree);       /* send the distance code */
               extra = extra_dbits[code];
               if (extra != 0) {
                  dist -= base_dist[code];
                  send_bits(s, dist, extra);   /* send the extra distance bits */
               }
            } /* literal or match pair ? */
         
         /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
         Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow");
         
         } while (lx < s->last_lit);
   
      send_code(s, END_BLOCK, ltree);
      s->last_eob_len = ltree[END_BLOCK].Len;
   }

/* ===========================================================================
 * Set the data type to ASCII or BINARY, using a crude approximation:
 * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
 * IN assertion: the fields freq of dyn_ltree are set and the total of all
 * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
 */
    local void set_data_type(deflate_state *s){
      int n = 0;
      unsigned ascii_freq = 0;
      unsigned bin_freq = 0;
      while (n < 7)        bin_freq += s->dyn_ltree[n++].Freq;
      while (n < 128)    ascii_freq += s->dyn_ltree[n++].Freq;
      while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq;
      s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII);
   }

/* ===========================================================================
 * Reverse the first len bits of a code, using straightforward code (a faster
 * method would use a table)
 * IN assertion: 1 <= len <= 15
 */
    local unsigned bi_reverse(
    unsigned code, /* the value to invert */
    int len)       /* its bit length */
   {
      register unsigned res = 0;
      do {
         res |= code & 1;
         code >>= 1, res <<= 1;
      } while (--len > 0);
      return res >> 1;
   }

/* ===========================================================================
 * Flush the bit buffer, keeping at most 7 bits in it.
 */
    local void bi_flush(deflate_state *s){
      if (s->bi_valid == 16) {
         put_short(s, s->bi_buf);
         s->bi_buf = 0;
         s->bi_valid = 0;
      } 
      else if (s->bi_valid >= 8) {
         put_byte(s, (Byte)s->bi_buf);
         s->bi_buf >>= 8;
         s->bi_valid -= 8;
      }
   }

/* ===========================================================================
 * Flush the bit buffer and align the output on a byte boundary
 */
    local void bi_windup(deflate_state *s){
      if (s->bi_valid > 8) {
         put_short(s, s->bi_buf);
      } 
      else if (s->bi_valid > 0) {
         put_byte(s, (Byte)s->bi_buf);
      }
      s->bi_buf = 0;
      s->bi_valid = 0;
   #ifdef DEBUG
    s->bits_sent = (s->bits_sent+7) & ~7;
   #endif
   }

/* ===========================================================================
 * Copy a stored block, storing first the length and its
 * one's complement if requested.
 */
    local void copy_block(
    deflate_state *s,
    charf    *buf,    /* the input data */
    unsigned len,     /* its length */
    int      header)  /* true if block header must be written */
   {
      bi_windup(s);        /* align on byte boundary */
      s->last_eob_len = 8; /* enough lookahead for inflate */
   
      if (header) {
         put_short(s, (ush)len);   
         put_short(s, (ush)~len);
      #ifdef DEBUG
        s->bits_sent += 2*16;
      #endif
      }
   #ifdef DEBUG
    s->bits_sent += (ulg)len<<3;
   #endif
      while (len--) {
         put_byte(s, *buf++);
      }
   }
